Thermal transfer element and process for forming organic electroluminescent devices

ABSTRACT

Disclosed are thermal transfer elements and processes for patterning solvent-coated layers and solvent-susceptible layers onto the same receptor substrate. These donor elements and methods are particularly suited for making organic electroluminescent devices and displays. The donor elements can include a substrate, an optional light-to-heat conversion layer, and a single or multicomponent transfer layer that can be imagewise transferred to a receptor to form an organic electroluminescent device, portions thereof, or components therefor. The methods offer advantages over conventional patterning techniques such as photolithography, and make it possible to fabricate new organic electroluminescent device constructions.

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/231,723, filed Jan. 15, 1999, which isincorporated herein by reference.

[0002] The present invention relates to methods and materials for makingand patterning organic electroluminescent devices as well as to organicelectroluminescent devices so made and to displays employing organicelectroluminescent devices.

BACKGROUND

[0003] Many miniature electronic and optical devices are formed usinglayers of different materials stacked on each other. These layers areoften patterned to produce the devices. Examples of such devices includeoptical displays in which each pixel is formed in a patterned array,optical waveguide structures for telecommunication devices, andmetal-insulator-metal stacks for semiconductor-based devices.

[0004] A conventional method for making these devices includes formingone or more layers on a receptor substrate and patterning the layerssimultaneously or sequentially to form the device. In many cases,multiple deposition and patterning steps are required to prepare theultimate device structure. For example, the preparation of opticaldisplays may require the separate formation of red, green, and bluepixels. Although some layers may be commonly deposited for each of thesetypes of pixels, at least some layers must be separately formed andoften separately patterned. Patterning of the layers is often performedby photolithographic techniques that include, for example, covering alayer with a photoresist, patterning the photoresist using a mask,removing a portion of the photoresist to expose the underlying layeraccording to the pattern, and then etching the exposed layer.

[0005] In some applications, it may be difficult or impractical toproduce devices using conventional photolithographic patterning. Forexample, the number of patterning steps may be too large for practicalmanufacture of the device. In addition, wet processing steps inconventional photolithographic patterning may adversely affectintegrity, interfacial characteristics, and/or electrical or opticalproperties of the previously deposited layers. It is conceivable thatmany potentially advantageous device constructions, designs, layouts,and materials are impractical because of the limitations of conventionalphotolithographic patterning. There is a need for new methods of formingthese devices with a reduced number of processing steps, particularlywet processing steps. In at least some instances, this may allow for theconstruction of devices with more reliability and more complexity.

SUMMARY OF THE INVENTION

[0006] The present invention provides new thermal transfer donorelements and methods of patterning using thermal transfer donorelements. The donors and methods of the present invention areparticularly suited to patterning solvent-coated materials on the samesubstrate as solvent-susceptible materials. This can be especiallyuseful in constructing organic electroluminescent displays and devicesas well as components for organic electroluminescent displays anddevices.

[0007] In one aspect, the present invention provides a method for makingan organic electroluminescent device that includes the step of thermallytransferring a light emitting polymer layer and a small molecule layerfrom one or more thermal transfer donor elements to a receptor so thatthe light emitting polymer layer and the small molecule layer aredisposed between an anode and a cathode on the receptor.

[0008] In another aspect, the present invention provides a thermaltransfer donor element for use in making organic electroluminescentdevices that includes, in the following order, a substrate, alight-to-heat conversion layer, an interlayer, and a thermal transferlayer that has, in the following order, a release layer, a cathodelayer, a light emitting polymer layer, a small molecule hole transportlayer, and an anode layer.

[0009] In another aspect, the present invention provides a method forpatterning a first material and a second material on a receptor, whichmethod includes selectively thermal transferring the first materialproximate to the second material on the receptor from a first donorelement, the first material being formed on the donor element bysolution coating using a solvent, the second material being incompatiblewith the solvent used to coat the first material, wherein at least oneof the first and second materials is an organic electroluminescentmaterial, an organic conductor, or an organic semiconductor.

[0010] In another aspect, the present invention provides a method forpatterning materials that includes forming a donor element that has asubstrate and a multicomponent thermal transfer layer, the thermaltransfer layer having at least a first layer that includes asolvent-coated material and a second layer that includes a solventsusceptible material, the solvent-susceptible material beingincompatible with the solvent used to coat the solvent-coated material,wherein the first layer is disposed between the second layer and thedonor substrate. Next, the thermal transfer layer of the donor is placedproximate a receptor and the multicomponent transfer layer isselectively thermally transferred from the donor element to thereceptor. At least one of the solvent-coated material and thesolvent-susceptible material is an organic electroluminescent material,an organic conductor, or an organic semiconductor.

[0011] In still another aspect, the present invention provides a methodfor patterning materials that includes the steps of thermallytransferring selected portions of a first transfer layer from a firstdonor element to a receptor, the first transfer layer containing a firstmaterial, the first material being solution-coated from a solvent ontothe first donor, and thermally transferring selected portions of asecond transfer layer from a second donor element t6 the receptor, thesecond transfer layer containing a second material, the second materialbeing incompatible with the solvent. At least one of the first andsecond materials is an organic electroluminescent material, an organicconductor, or an organic semiconductor.

[0012] In yet another aspect, the present invention provides a methodfor making a thermal transfer donor element, which method includesforming a donor element that has a donor substrate and a transfer layer,the transfer layer being formed by (a) solution coating a first materialusing a solvent, (b) drying the first material to substantially removethe solvent, and (c) depositing a second material such that the firstmaterial is disposed between the donor substrate and the secondmaterial, the second material being incompatible with the solvent usedto coat the first material.

[0013] In another aspect, the present invention provides an organicelectroluminescent display that includes a first organicelectroluminescent device disposed on a display substrate, the firstorganic electroluminescent device having an emitter layer that is alight emitting polymer, and a second organic electroluminescent devicedisposed on the display substrate, the second organic electroluminescentdevice having an emitter layer that is an organic small moleculematerial.

[0014] In another aspect, the present invention provides an organicelectroluminescent display that includes an organic electroluminescentdevice disposed on a display substrates the organic electroluminescentdevice including, in the following order from the substrate, a firstelectrode, a small molecule charge transport layer, a polymer emitterlayer, and a second electrode.

[0015] The above summary of the present invention is not intended todescribe each disclosed embodiment or every implementation of thepresent invention. The Figures and the detailed description which followmore particularly exemplify these embodiments.

[0016] It should be understood that by specifying an order in thepresent document (e.g., order of steps to be performed, order of layerson a substrate, etc.), it is not meant to preclude intermediates betweenthe items specified, as long as the items appear in the order asspecified.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention may be more completely understood in considerationof the following detailed description of various embodiments of theinvention in connection with the accompanying drawings, in which:

[0018]FIG. 1A is a schematic cross-section of one example of a thermaltransfer element according to the invention;

[0019]FIG. 1B is a schematic cross-section of a second example of athermal transfer element according to the invention;

[0020]FIG. 1C is a schematic cross-section of a third example of athermal transfer element according to the invention;

[0021]FIG. 1D is a schematic cross-section of a fourth example of athermal transfer element according to the invention;

[0022]FIG. 2A is a schematic cross-section of a first example of atransfer layer, according to the invention, for use in any of thethermal transfer elements of FIGS. 1A to 1D;

[0023]FIG. 2B is a schematic cross-section of a second example of atransfer layer, according to the invention, for use in any of thethermal transfer elements of FIGS. 1A to 1D;

[0024]FIG. 2C is a schematic cross-section of a third example of atransfer layer, according to the invention, for use in any of thethermal transfer elements of FIGS. 1A to 1D;

[0025]FIG. 2D is a schematic cross-section of a fourth example of atransfer layer, according to the invention, for use in any of thethermal transfer elements of FIGS. 1A to 1D;

[0026]FIG. 2E is a schematic cross-section of a fifth example of atransfer layer, according to the invention, for use in any of thethermal transfer elements of FIGS. 1A to 1D;

[0027]FIG. 3A is a schematic cross-section of an example of a transferlayer, according to the invention, for use in forming an organicelectroluminescent device;

[0028]FIG. 3B is a schematic cross-section of a second example of atransfer layer, according to the invention, for use in forming anorganic electroluminescent device;

[0029]FIGS. 4A to 4C are cross-sectional views illustrating steps in oneexample of a process for forming a display device according to theinvention;

[0030]FIGS. 5A and 5B are cross-sectional views illustrating steps inone example of a process for forming a display device according to theinvention; and

[0031]FIG. 6 is a partial top view of a display device made according toa method of the present invention.

[0032] While the invention is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

[0033] The present invention is applicable to the formation or partialformation of devices and other objects using thermal transfer processesand thermal transfer donor elements for forming the devices or otherobjects. As a particular example, a thermal transfer element can beformed for making, at least in part, an organic electroluminescent (OEL)device or array of devices, and components for use in OEL displays. Thiscan be accomplished, for example, by thermal transfer of a single or amulticomponent transfer unit of a thermal transfer element. It will berecognized that single layer and multilayer transfers can be used toform other devices and objects. While the present invention is not solimited, an appreciation of various aspects of the invention will begained through a discussion of the examples provided below.

[0034] Materials can be patterned onto substrates by selective thermaltransfer of the materials from one or more thermal transfer elements. Athermal transfer element can be heated by application of directed heaton a selected portion of the thermal transfer element. Heat can begenerated using a heating element (e.g., a resistive heating element),converting radiation (e.g., a beam of light) to heat, and/or applying anelectrical current to a layer of the thermal transfer element togenerate heat. In many instances, thermal transfer using light from, forexample, a lamp or laser, is advantageous because of the accuracy andprecision that can often be achieved. The size and shape of thetransferred pattern (e.g., a line, circle, square, or other shape) canbe controlled by, for example, selecting the size of the light beam, theexposure pattern of the light beam, the duration of directed beamcontact with the thermal transfer element, and the materials of thethermal transfer element.

[0035] A thermal transfer element can include a transfer layer that canbe used to form various elements and devices, or portions thereof.Exemplary materials and transfer layers include those that can be usedto form elements, devices, and portions thereof that are useful inelectronic displays. While the examples used in the present inventionmost often focus on OEL devices and displays, transfer of materials fromthermal transfer elements can also be used to form, at least in part,electronic circuitry, resistors, capacitors, diodes, rectifiers,electroluminescent lamps, memory elements, field effect transistors,bipolar transistors, unijunction transistors MOS transistors,metal-insulator-semiconductor transistors, organic transistors, chargecoupled devices, insulator-metal-insulator stacks, organicconductor-metal-organic conductor stacks, integrated circuits,photodetectors, lasers, lenses, waveguides, gratings, holographicelements, filters (e.g., add-drop filters, gain-flattening filters,cut-off filters, and the like), mirrors, splitters, couplers, combiners,modulators, sensors (e.g., evanescent sensors, phase modulation sensors,interferometric sensors, and the like), optical cavities, piezoelectricdevices, ferroelectric devices, thin film batteries, or combinationsthereof; for example, the combination of field effect transistors andorganic electroluminescent lamps as an active matrix array for anoptical display. Other items may be formed by transferring amulticomponent transfer unit and/or a single layer.

[0036] Thermal transfer using light can often provide better accuracyand quality control for very small devices, such as small optical andelectronic devices, including, for example, transistors and othercomponents of integrated circuits, as well as components for use in adisplay, such as electroluminescent lamps and control circuitry.Moreover, thermal transfer using light may, at least in some instances,provide for better registration when forming multiple devices over anarea that is large compared to the device size. As an example,components of a display, which has many pixels, can be formed using thismethod.

[0037] In some instances, multiple thermal transfer elements may be usedto form a device or other object, or to form adjacent devices, otherobjects, or portions thereof The multiple thermal transfer elements mayinclude thermal transfer elements with multicomponent transfer units andthermal transfer elements that transfer a single layer. For example, adevice or other object may be formed using one or more thermal transferelements with multicomponent transfer units and/or one or more thermaltransfer elements that each can be used to transfer a single layer or amultilayer unit.

[0038] Thermal transfer of one or more layers to form a device or anarray of devices can also be useful, for example, to reduce or eliminatewet processing steps of processes such as photolithographic patterning,which are used to form many electronic and optical devices. Thermaltransfer to pattern layers from donor elements can also be useful tode-couple layer coating steps from patterning steps, for example wheresuch coupling can limit the types of layered structures, or the types ofadjacent structures, that can be patterned. In conventional patterningprocesses such as photolithography, ink-jet, screen printing, andvarious mask-based techniques, layers are typically coated directly ontothe substrate on which patterning occurs. Patterning can take placesimultaneously with coating (as for ink-jet, screen printing, and somemask-based processes) or subsequent to coating via etching or anotherremoval technique. A difficulty with such conventional approaches isthat solvents used to coat materials, and/or etching processes used topattern materials, can damage, dissolve, penetrate, and/or renderinoperable previously coated or patterned layers or materials.

[0039] In the present invention, materials can be coated onto thermaltransfer donor elements to form the transfer layers of the donorelements. The transfer layer materials can then be patterned viaselective thermal transfer from the donor to a receptor. Coating onto adonor followed by patterning via selective transfer represents ade-coupling of layer coating steps from patterning steps. An advantageof de-coupling coating and patterning steps is that materials can bepatterned on top of or next to other materials that would be difficultto pattern, if possible at all, using conventional patterning processes.For example, in methods of the present invention a solvent-coated layercan be patterned on top of a solvent-susceptible material that would bedissolved, attacked, penetrated, and/or rendered inoperable for itsintended purpose in the presence of the solvent had the solvent-coatedlayer been coated directly on the solvent-susceptible material.

[0040] A transfer layer of a donor element can be made bysolvent-coating a first material on the donor, suitably drying thecoating, and then depositing a second layer that includes material thatmay be susceptible to the solvent used to coat the first material.Damage to the second layer can be minimized or eliminated byevaporation, or otherwise removal, of much or most of the solvent beforecoating of the second layer. Upon thermal transfer of thismulticomponent transfer layer from the donor element to a receptor, thesecond layer becomes positioned between the receptor and thesolvent-coated first material. Thermal transfer of multiple layer unitsresults in a reverse ordering of the transferred layers on the receptorrelative to the ordering on the donor element. Because of this,solvent-susceptible layers can be pattered underneath solvent-coatedlayers. In addition, the layers need not be transferred together as amultiple layer unit. The solvent-susceptible material(s) can bepatterned by any suitable method, including thermal transfer from adonor, followed by another thermal transfer step using another donor totransfer the solvent-coated material(s).

[0041] The same holds for patterned thermal transfer of solvent-coatedmaterials next to, but not necessarily in contact with, materials orlayers on a receptor that may be incompatible with the solvent. As willbe discussed in more detail below, the formation of OEL devices providesparticularly suited examples.

[0042] With these general concepts of the present invention in mind,exemplary donor elements, thermal transfer methods, and devices made bythermal transfer methods will now be described.

[0043] One example of a suitable thermal transfer element 100 isillustrated in FIG. 1A. The thermal transfer element 100 includes adonor substrate 102, an optional primer layer 104, a light-to-heatconversion (LTHC) layer 106, an optional interlayer 108, an optionalrelease layer 112, and a transfer layer 110. Directed light from alight-emitting source, such as a laser or lamp, can be used toilluminate the thermal transfer element 100 according to a pattern. TheLTHC layer 106 contains a radiation absorber that converts light energyto heat energy. The conversion of the light energy to heat energyresults in the transfer of a portion of the transfer layer 110 to areceptor (not shown).

[0044] Another example of a thermal transfer element 120 includes adonor substrate 122, an LTHC layer 124, an interlayer 126, and atransfer layer 128, as illustrated in FIG. 1B. Another suitable thermaltransfer element 140 includes a donor substrate 142, an LTHC layer 144,and a transfer layer 146, as illustrated in FIG. 1C. Yet another exampleof a thermal transfer element 160 includes a donor substrate 162 and atransfer layer 164, as illustrated in FIG. 1D, with an optionalradiation absorber disposed in the donor substrate 162 and/or transferlayer 164 to convert light energy to heat energy. Alternatively, thethermal transfer element 160 may be used without a radiation absorberfor thermal transfer of the transfer layer 164 using a heating element,such as a resistive heating element, that contacts the thermal transferelement to selectively heat the thermal transfer element and transferthe transfer layer according to a pattern. A thermal transfer element160 without radiation absorber may optionally include a release layer,an interlayer, and/or other layers (e.g., a coating to prevent stickingof the resistive heating element) used in the art.

[0045] For thermal transfer using radiation (e.g., light), a variety ofradiation-emitting sources can be used in the present invention. Foranalog techniques (e.g., exposure through a mask), high-powered lightsources (e.g., xenon flash lamps and lasers) are useful. For digitalimaging techniques, infrared, visible, and ultraviolet lasers areparticularly useful. Suitable lasers include, for example, high power(≧100 mW) single mode laser diodes, fiber-coupled laser diodes, anddiode-pumped solid state lasers (e.g., Nd:YAG and Nd:YLF). Laserexposure dwell times can be in the range from, for example, about 0.1 to100 microseconds and laser fluences can be in the range from, forexample, about 0.01 to about 1 J/cm².

[0046] When high spot placement accuracy is required (e.g. for highinformation full color display applications) over large substrate areas,a laser is particularly useful as the radiation source. Laser sourcesare compatible with both large rigid substrates such as 1 m×1 m×1.1 mmglass, and continuous or sheeted film substrates, such as 100 μmpolyimide sheets.

[0047] Resistive thermal print heads or arrays may be used, for example,with simplified donor film constructions lacking an LTHC layer andradiation absorber. This may be particularly useful with smallersubstrate sizes (e.g., less than approximately 30 cm in any dimension)or for larger patterns, such as those required for alphanumericsegmented displays.

[0048] During imaging, the thermal transfer element is typically broughtinto intimate contact with a receptor. In at least some instances,pressure or vacuum are used to hold the thermal transfer element inintimate contact with the receptor. A radiation source is then used toheat the LTHC layer (and/or other layer(s) containing radiationabsorber) in an imagewise fashion (e.g., digitally or by analog exposurethrough a mask) to perform imagewise transfer of the transfer layer fromthe thermal transfer element to the receptor according to a pattern.

[0049] Alternatively, a heating element, such as a resistive heatingelement, may be used to transfer the multicomponent transfer unit. Thethermal transfer element is selectively contacted with the heatingelement to cause thermal transfer of a portion of the transfer layeraccording to a pattern. In another embodiment, the thermal transferelement may include a layer that can convert an electrical currentapplied to the layer into heat.

[0050] Typically, the transfer layer is transferred to the receptorwithout transferring any of the other layers of the thermal transferelement, such as the optional interlayer and the LTHC layer. Thepresence of the optional interlayer may eliminate or reduce the transferof the LTHC layer to the receptor and/or reduce distortion in thetransferred portion of the transfer layer. Preferably, under imagingconditions, the adhesion of the interlayer to the LTHC layer is greaterthan the adhesion of the interlayer to the transfer layer. In someinstances, a reflective or an absorptive interlayer can be used toattenuate the level of imaging radiation transmitted through theinterlayer and reduce any damage to the transferred portion of thetransfer layer that may result from interaction of the transmittedradiation with the transfer layer and/or the receptor. This isparticularly beneficial in reducing thermal damage which may occur whenthe receptor is highly absorptive of the imaging radiation.

[0051] Large thermal transfer elements can be used, including thermaltransfer elements that have length and width dimensions of a meter ormore. In operation, a laser can be rastered or otherwise moved acrossthe large thermal transfer element, the laser being selectively operatedto illuminate portions of the thermal transfer element according to adesired pattern. Alternatively, the laser may be stationary and thethermal transfer element moved beneath the laser.

[0052] Thermal transfer donor substrates can be polymer films. Onesuitable type of polymer film is a polyester film, for example,polyethylene terephthalate or polyethylene naphthalate films. However,other films with sufficient optical properties (if light is used forheating and transfer), including high transmission of light at aparticular wavelength, as well as sufficient mechanical and thermalstability for the particular application, can be used. The donorsubstrate, in at least some instances, is flat so that uniform coatingscan be formed thereon. The donor substrate is also typically selectedfrom materials that remain stable despite heating of the LTHC layer. Thetypical thickness of the donor substrate ranges from 0.025 to 0.15 mm,preferably 0.05 to 0.1 mm, although thicker or thinner donor substratesmay be used.

[0053] Typically, the materials used to form the donor substrate and theLTHC layer are selected to improve adhesion between the LTHC layer andthe donor substrate. An optional priming layer can be used to increaseuniformity during the coating of subsequent layers and also increase theinterlayer bonding strength between the LTHC layer and the donorsubstrate. One example of a suitable substrate with primer layer isavailable from Teijin Ltd. (Product No. HPE100, Osaka, Japan).

[0054] For radiation-induced thermal transfer a light-to-heat conversion(LTHC) layer is typically incorporated within the thermal transferelement to couple the energy of light radiated from a light-emittingsource into the thermal transfer element. The LTHC layer preferablyincludes a radiation absorber that absorbs incident radiation (e.g., laser light) and converts at least a portion of the incident radiation intoheat to enable transfer of the transfer layer from the thermal transferelement to the receptor. In some embodiments, there is no separate LTHClayer and, instead, the radiation absorber is disposed in another layerof the thermal transfer element, such as the donor substrate or thetransfer layer. In other embodiments, the thermal transfer elementincludes an LTHC layer and also includes additional radiationabsorber(s) disposed in one or more of the other layers of the thermaltransfer element, such as, for example, the donor substrate or thetransfer layer. In yet other embodiments, the thermal transfer elementdoes not include an LTHC layer or radiation absorber and the transferlayer is transferred using a heating element that contacts the thermaltransfer element.

[0055] Typically, the radiation absorber in the LTHC layer (or otherlayers) absorbs light in the infrared, visible, and/or ultravioletregions of the electromagnetic spectrum. The radiation absorber istypically highly absorptive of the selected imaging radiation, providingan optical density at the wavelength of the imaging radiation in therange of 0.2 to 3, and preferably from 0.5 to 2. Suitable radiationabsorbing materials can include, for example, dyes (e.g., visible dyes,ultraviolet dyes, infrared dyes, fluorescent dyes, andradiation-polarizing dyes), pigments, metals, metal compounds, metalfilms, and other suitable absorbing materials. Examples of suitableradiation absorbers can include carbon black, metal oxides, and metalsulfides. One example of a suitable LTHC layer can include a pigment,such as carbon black, and a binder, such as an organic polymer. Anothersuitable LTHC layer can include metal or metal/metal oxide formed as athin film, for example, black aluminum (i.e., a partially oxidizedaluminum having a black visual appearance). Metallic and metal compoundfilms may be formed by techniques, such as, for example, sputtering andevaporative deposition. Particulate coatings may be formed using abinder and any suitable dry or wet coating techniques.

[0056] Radiation absorber material can be uniformly disposed throughoutthe LTHC layer or can be non-homogeneously distributed. For example, asdescribed in co-assigned U.S. patent application Ser. No. ______(attorney docket number 54992USA9A, entitled “Thermal Mass TransferDonor Elements”, the disclosure of which is wholly incorporated intothis document, non-homogeneous LTHC layers can be used to controltemperature profiles in donor elements. This can give rise to thermaltransfer elements that have higher transfer sensitivities (e.g., betterfidelity between the intended transfer patterns and actual transferpatterns).

[0057] Dyes suitable for use as radiation absorbers in an LTHC layer maybe present in particulate form, dissolved in a binder material, or atleast partially dispersed in a binder material. When dispersedparticulate radiation absorbers are used, the particle size can be, atleast in some instances, about 10 μm or less, and may be about 1 μm orless. Suitable dyes include those dyes that absorb in the IR region ofthe spectrum. Examples of such dyes may be found in Matsuoka, M.,“Infrared Absorbing Matcrials”, Plenum Press, New York, 1990; Matsuoka,M., Absorption Spectra of Dyes for Diode Lasers, Bunshin Publishing Co.,Tokyo, 1990, U.S. Pat. Nos. 4,722,583; 4,833,124; 4,912,083; 4,942,141;4,948,776; 4,948,778; 4,950,639; 4,940,640; 4,952,552; 5,023,229;5,024,990; 5,156,938; 5,286,604; 5,340,699; 5,351,617; 5,360,694; and5,401,607; European Patent Nos. 321,923 and 568,993; and Beilo, K. A. etal., J. Chem. Soc., Chem. Commun., 1993, 452-454 (1993), all of whichare herein incorporated by reference. IR absorbers marketed by GlendaleProtective Technologies, Inc., Lakeland, Fla., under the designationCYASORB IR-99, IR-126 and IR-165 may also be used. A specific dye may bechosen based on factors such as, solubility in, and compatibility with,a specific binder and/or coating solvent, as well as the wavelengthrange of absorption.

[0058] Pigmentary materials may also be used in the LTHC layer asradiation absorbers. Examples of suitable pigments include carbon blackand graphite, as well as phthalocyanines, nickel dithiolenes, and otherpigments described in U.S. Pat. Nos. 5,166,024 and 5,351,617,incorporated herein by reference. Additionally, black azo pigments basedon copper or chromium complexes of, for example, pyrazolone yellow,dianisidine red, and nickel azo yellow can be useful. Inorganic pigmentscan also be used, including, for example, oxides and sulfides of metalssuch as aluminum, bismuth, tin, indium, zinc, titanium, chromium,molybdenum, tungsten, cobalt, iridium, nickel, palladium, platinum,copper, silver, gold, zirconium, iron, lead, and tellurium. Metalborides, carbides, nitrides, carbonitrides, bronze-structured oxides,and oxides structurally related to the bronze family (e.g., WO_(2.9))may also be used.

[0059] Metal radiation absorbers may be used, either in the form ofparticles, as described for instance in U.S. Pat. No. 4,252,671,incorporated herein by reference, or as films, as disclosed in U.S. Pat.No. 5,256,506, incorporated herein by reference. Suitable metalsinclude, for example, aluminum, bismuth, tin, indium, tellurium andzinc.

[0060] As indicated, a particulate radiation absorber may be disposed ina binder. The weight percent of the radiation absorber in the coating,excluding the solvent in the calculation of weight percent, is generallyfrom 1 wt. % to 30 wt. %, preferably from 3 wt. % to 20 wt. %, and mostpreferably from 5 wt. % to 15 wt. %, depending on the particularradiation absorber(s) and binder(s) used in the LTHC.

[0061] Suitable binders for use in the LTHC layer include film-formingpolymers, such as, for example, phenolic resins (e.g., novolak andresole resins), polyvinyl butyral resins, polyvinyl acetates, polyvinylacetals, polyvinylidene chlorides, polyacrylates, cellulosic ethers andesters, nitrocelluloses, and polycarbonates. Suitable binders mayinclude monomers, oligomers, or polymers that have been or can bepolymerized or crosslinked. In some embodiments, the binder is primarilyformed using a coating of crosslinkable monomers and/or oligomers withoptional polymer. When a polymer is used in the binder, the binderincludes 1 to 50 wt. %, preferably, 10 to 45 wt. %, polymer (excludingthe solvent when calculating wt. %).

[0062] Upon coating on the donor substrate, the monomers, oligomers, andpolymers may be crosslinked to form the LTHC. In some instances, ifcrosslinking of the LTHC layer is too low, the LTHC layer may be damagedby the heat and/or permit the transfer of a portion of the LTHC layer tothe receptor with the transfer layer.

[0063] The inclusion of a thermoplastic resin (e.g., polymer) mayimprove, in at least some instances, the performance (e.g., transferproperties and/or coatability) of the LTHC layer. It is thought that athermoplastic resin may improve the adhesion of the LTHC layer to thedonor substrate. In one embodiment, the binder includes 25 to 50 wt. %(excluding the solvent when calculating weight percent) thermoplasticresin, and, preferably, 30 to 45 wt. % thermoplastic resin, althoughlower amounts of thermoplastic resin may be used (e.g., 1 to 15 wt. %).The thermoplastic resin is typically chosen to be compatible (i.e., forma one-phase combination) with the other materials of the binder. Asolubility parameter can be used to indicate compatibility, PolymerHandbook, J. Brandrup, ed., pp. VII 519-557 (1989), incorporated hereinby reference. In at least some embodiments, a thermoplastic resin thathas a solubility parameter in the range of 9 to 13 (cal/cm³)^(½),preferably, 9.5 to 12 (cal/cm³)^(½), is chosen for the binder. Examplesof suitable thermoplastic resins include polyacrylics, styrene-acrylicpolymers and resins, and polyvinyl butyral.

[0064] Conventional coating aids, such as surfactants and dispersingagents, may be added to facilitate the coating process. The LTHC layermay be coated onto the donor substrate using a variety of coatingmethods known in the art. A polymeric or organic LTHC layer is coated,in at least some instances, to a thickness of 0.05 μm to 20 μm,preferably, 0.5 μm to 10 μm, and, most preferably, 1 μm to 7 μm. Aninorganic LTHC layer is coated, in at least some instances, to athickness in the range of 0.001 to 10 μm, and preferably, 0.002 to 1 μm.

[0065] An optional interlayer may be disposed between the LTHC layer andtransfer layer in thermal transfer elements to minimize damage andcontamination of the transferred portion of the transfer layer and mayalso reduce distortion in the transferred portion of the transfer layer.The interlayer may also influence the adhesion of the transfer layer tothe rest of the thermal transfer element. Typically, the interlayer hashigh thermal resistance. Preferably, the interlayer does not distort orchemically decompose under the imaging conditions, particularly to anextent that renders the transferred image non-functional. The interlayertypically remains in contact with the LTHC layer during the transferprocess and is not substantially transferred with the transfer layer.

[0066] Suitable interlayers include, for example, polymer films, metallayers (e.g., vapor deposited metal layers), inorganic layers (e.g.,sol-gel deposited layers and vapor deposited layers of inorganic oxides(e.g., silica, titania, and other metal oxides)), and organic/inorganiccomposite layers. Organic materials suitable as interlayer materialsinclude both thermoset and thermoplastic materials. Suitable thermosetmaterials include resins that may be crosslinked by heat, radiation, orchemical treatment including, but not limited to, crosslinked orcrosslinkable polyacrylates, polymethacrylaies, polyesters, epoxies, andpolyurethanes. The thermoset materials may be coated onto the LTHC layeras, for example, thermoplastic precursors and subsequently crosslinkedto form a crosslinked interlayer.

[0067] Suitable thermoplastic materials include, for example,polyacrylates, polymethacrylates, polystyrenes, polyurethanes,polysulfones, polyesters, and polyimides. These thermoplastic organicmaterials may be applied via conventional coating techniques (forexample, solvent coating, spray coating, or extrusion coating).Typically, the glass transition temperature (T_(g)) of thermoplasticmaterials suitable for use in the interlayer is 25° C. or greater,preferably 50° C. or greater, more preferably 100° C. or greater, and,most preferably, 150° C. or greater. The interlayer may be eithertransmissive, absorbing, reflective, or some combination thereof, at theimaging radiation wavelength.

[0068] Inorganic materials suitable as interlayer materials include, forexample, metals, metal oxides, metal sulfides, and inorganic carboncoatings, including those materials that are highly transmissive orreflective at the imaging light wavelength. These materials may beapplied to the light-to-heat-conversion layer via conventionaltechniques (e.g., vacuum sputtering, vacuum evaporation, or plasma jetdeposition).

[0069] The interlayer may provide a number of benefits. The interlayermay be a barrier against the transfer of material from the light-to-heatconversion layer. It may also modulate the temperature attained in thetransfer layer so that thermally unstable materials can be transferred.The presence of an interlayer may also result in improved plastic memoryin the transferred material.

[0070] The interlayer may contain additives, including, for example,photoinitiators, surfactants, pigments, plasticizers, and coating aids.The thickness of the interlayer may depend on factors such as, forexample, the material of the interlayer, the material of the LTHC layer,the material of the transfer layer, the wavelength of the imagingradiation, and the duration of exposure of the thermal transfer elementto imaging radiation. For polymer interlayers, the thickness of theinterlayer typically is in the range of 0.05 μm to 10 μm, preferably,from about 0.1 μm to 4 μm, more preferably, 0.5 to 3 μm, and, mostpreferably, 0.8 to 2 μm. For inorganic interlayers (e.g., metal or metalcompound interlayers), the thickness of the interlayer typically is inthe range of 0.005 m to 10 μm, preferably, from about 0.01 μm to 3 μm,and, more preferably, from about 0.02 to 1 μm.

[0071] Thermal transfer elements can include an optional release layer.The optional release layer typically facilitates release of the transferlayer from the rest of the thermal transfer element (e.g., theinterlayer and/or the LTHC layer) upon heating of the thermal transferelement, for example, by a light-emitting source or a heating element.In at least some cases, the release layer provides some adhesion of thetransfer layer to the rest of the thermal transfer element prior toexposure to heat. Suitable release layers include, for example,conducting and non-conducting thermoplastic polymers, conducting andnon-conducting filled polymers, and/or conducting and non-conductingdispersions. Examples of suitable polymers include acrylic polymers,polyanilines, polythiophenes, poly(phenylenevinylenes), polyacetylenes,and other conductive organic materials, such as those listed in Handbookof Conductive Molecules and Polymers, Vols. 1-4, H. S. Nalwa, ed., JohnWiley and Sons, Chichester (1997), incorporated herein by reference.Examples of suitable conductive dispersions include inks containingcarbon black, graphite, ultrafine particulate indium tin oxide,ultrafine antimony tin oxide, and commercially available materials fromcompanies such as Nanophase Technologies Corporation (Burr Ridge, Ill.)and Metech (Elverson, Pa.). Other suitable materials for the releaselayer include sublimable insulating materials and sublimablesemiconducting materials (such as phthalocyanines), including, forexample, the materials described in U.S. Pat. No. 5,747,217,incorporated herein by reference.

[0072] The release layer may be part of the transfer layer or a separatelayer. All or a portion of the release layer may be transferred with thetransfer layer. Alternatively, most or substantially all of the releaselayer can remain with the donor substrate when the transfer layer istransferred. In some instances, for example with a release layer thatincludes a sublimable material, a portion of the release layer may bedissipated during the transfer process.

[0073] The transfer layers of thermal transfer elements of the presentinvention can include one or more layers for transfer to a receptor.These one or more layers may be formed using organic, inorganic,organometallic, and other materials. Although the transfer layer isdescribed and illustrated as having one or more discrete layers, it willbe appreciated that, at least in some instances where more than onelayer is used, there may be an interfacial region that includes at leasta portion of each layer. This may occur, for example, if there is mixingof the layers or diffusion of material between the layers before,during, or after transfer of the transfer layer. In other instances,individual layers may be completely or partially mixed before, during,or after transfer of the transfer layer. In any case, these structureswill be referred to as including more than one independent layer,particularly if different functions of the device are performed by thedifferent regions.

[0074] One advantage of using a multicomponent transfer unit,particularly if the layers do not mix, is that the important interfacialcharacteristics of the layers in the multicomponent transfer unit can beproduced when the thermal transfer unit is prepared and, preferably,retained during transfer.

[0075] One example of a transfer layer includes a single ormulticomponent transfer unit that is used to form at least part of amultilayer device, such as an OEL device, or another device used inconnection with OEL devices, on a receptor. In some cases, the transferlayer may include all of the layers needed to form an operative device.In other cases, the transfer layer may include fewer than all the layersneeded to form an operative device, the other layers being formed viatransfer from one or more other donor elements or via some othersuitable transfer or patterning method. In still other instances, one ormore layers of a device may be provided on the receptor, the remaininglayer or layers being included in the transfer layer of one or moredonor elements. Alternatively, one or more additional layers of a devicemay be transferred onto the receptor after the transfer layer has beenpatterned. In some instances, the transfer layer is used to form only asingle layer of a device.

[0076] In one embodiment, an exemplary transfer layer includes amulticomponent transfer unit that is capable of forming at least twolayers of a multilayer device. These two layers of the multilayer deviceoften correspond to two layers of the transfer layer. In this example,one of the layers that is formed by transfer of the multicomponenttransfer unit can be an active layer (i.e., a layer that acts as aconducting, semiconducting, electron blocking, hole blocking, lightproducing (e.g., luminescing, light emitting, fluorescing, orphosphorescing), electron producing, or hole producing layer). A secondlayer that is formed by transfer of the multicomponent transfer unit canbe another active layer or an operational layer (i.e., a layer that actsas an insulating, conducting, semiconducting, electron blocking, holeblocking, light producing, electron producing, hole producing, lightabsorbing, reflecting, diffracting, phase retarding, scattering,dispersing, or diffusing layer in the device). The second layer can alsobe a non-operational layer (i.e., a layer that does not perform afunction in the operation of the device, but is provided, for example,to facilitate transfer and/or adherence of the transfer unit to thereceptor substrate during patterning). The multicomponent transfer unitmay also be used to form additional active layers, operational layers,and/or non-operational layers.

[0077] The transfer layer may include an adhesive layer disposed on anouter surface of the transfer layer to facilitate adhesion to thereceptor. The adhesive layer may be an operational layer, for example,if the adhesive layer conducts electricity between the receptor and theother layers of the transfer layer, or a non-operational layer, forexample, if the adhesive layer only adheres the transfer layer to thereceptor. The adhesive layer may be formed using, for example,thermoplastic polymers, including conducting and non-conductingpolymers, conducting and non-conducting filled polymers, and/orconducting and non-conducting dispersions. Examples of suitable polymersinclude acrylic polymers, polyanilines, polythiophenes,poly(phenylenevinylenes), polyacetylenes, and other conductive organicmaterials such as those listed in Handbook of Conductive Molecules andPolymers, Vols. 1-4, H. S. Nalwa, ed., John Wiley and Sons, Chichester(1997), incorporated herein by reference. Examples of suitableconductive dispersions include inks containing carbon black, graphite,carbon nanotubes, ultrafine particulate indium tin oxide, ultrafineantimony tin oxide, and commercially available materials from companiessuch as Nanophase Technologies Corporation (Burr Ridge, Ill.) and Metech(Elverson, Pa.). Conductive adhesive layers can also include vapor orvacuum deposited organic conductors such asN,N′-bis(1-naphthyl)-N,N′-diphenylbenzidine (also known as NPB).

[0078] The transfer layer may also include a release layer disposed onthe surface of the transfer layer that is in contact with the rest ofthe thermal transfer element. As described above, this release layer maypartially or completely transfer with the remainder of the transferlayer, or substantially all of the release layer may remain with thethermal transfer element, or the release layer may dissipate in whole orin part, upon transfer of the transfer layer. Suitable release layersare described above.

[0079] Although the transfer layer may be formed with discrete layers,it will be understood that, in at least some embodiments, the transferlayer may include layers that have multiple components and/or multipleuses in the device. It will also be understood that, at least in someembodiments, two or more discrete layers may be melted together duringtransfer or otherwise mixed or combined. In any case, these layers,although mixed or combined, will be referred to as individual layers.

[0080] One example of a transfer layer 170, illustrated in FIG. 2A,includes a conductive metal or metal compound layer 172 and a conductivepolymer layer 174. Transfer layer 170 may be arranged so that eitherlayer 172 or layer 174 is the outer layer of the donor (i.e., layer forcontacting receptor (not shown) upon transfer). The conductive polymerlayer 174 may also act, at least in part, as an adhesive layer tofacilitate transfer to the receptor or elements or layers previouslyformed on the receptor when the conductive polymer layer 174 is theouter layer.

[0081] A second example of a transfer layer 180, illustrated in FIG. 2B,includes a release layer 182, followed by a conductive metal or metalcompound layer 184, and then a conductive or non-conductive polymerlayer 186 for contact with a receptor (not shown). In other embodiments,the ordering of layers 184 and 186 can be reversed so that layer 184 isthe outer layer.

[0082] A third example of a transfer layer 190, illustrated in FIG. 2C,includes a conductive inorganic layer 191 (for example, vapor depositedindium tin oxide), a conductive or non-conductive polymer layer 192, andan optional release layer (not shown). Either layer 191 or layer 192 canbe the outer layer.

[0083] A fourth example of a transfer layer 195, illustrated in FIG. 2D,consists of a multilayer metal stack 196 of alternating metals 197, 198,such as gold-aluminum-gold, and a conductive or non-conductive polymerlayer 199 for contact with a receptor.

[0084] A fifth example of a transfer layer 175, illustrated in FIG. 2E,includes a solvent-coated layer 176 and an adjacent layer 177 that issusceptible to the solvent used to coat layer 176. Layer 177 can beformed on solvent-coated layer 176 after layer solvent-coated 176 iscoated onto the donor element, and preferably dried to substantiallyremove the solvent. Transfer layer 175 can include additional layers(not shown) disposed above layer 177, below layer 176, or between layers176 and 177, including release and adhesion layers. When transfer layer175 is transferred to a receptor (not shown), layer 177 will be disposedbetween the receptor and solvent-coated layer 176.

[0085] The transfer of a one or more single or multicomponent transferunits to form at least a portion of an OEL (organic electroluminescent)device provides a particularly illustrative, non-limiting example of theformation of an active device using a thermal transfer element. In atleast some instances, an OEL device includes a thin layer, or layers, ofone or more suitable organic materials sandwiched between a cathode andan anode. Electrons are injected into the organic layer(s) from thecathode and holes are injected into the organic layer(s) from the anode.As the injected charges migrate towards the oppositely chargedelectrodes, they may recombine to form electron-hole pairs which aretypically referred to as excitons. These excitons, or excited statespecies, may emit energy in the form of light as they decay back to aground state (see, for example, T. Tsutsui, MRS Bulletin, 22, 39-45(1997), incorporated herein by reference).

[0086] Illustrative examples of OEL device constructions includemolecularly dispersed polymer devices where charge carrying and/oremitting species are dispersed in a polymer matrix (see J. Kido “OrganicElectroluminescent devices Based on Polymeric Materials”, Trends inPolymer Science, 2, 350-355 (1994), incorporated herein by reference),conjugated polymer devices where layers of polymers such aspolyphenylene vinylene act as the charge carrying and emitting species(see J. J. M. Halls et al., Thin Solid Films, 276, 13-20 (1996), hereinincorporated by reference), vapor deposited small moleculeheterostructure devices (see U.S. Pat. No. 5,061,569 and C. H. Clien etal., “Recent Developments in Molecular Organic ElectroluminescentMaterials”, Macromolecular Symposia, 125, 1-48 (1997), hereinincorporated by reference), light emitting electrochemical cells (see Q.Pei et al., J. Amer. Chem. Soc., 118, 3922-3929 (1996), hereinincorporated by reference), and vertically stacked organiclight-emitting diodes capable of emitting light of multiple wavelengths(see U.S. Pat. No. 5,707,745 and Z. Shen et al., Science, 276, 2009-2011(1997), herein incorporated by reference).

[0087] As used herein, the term “small molecule” refers to anon-polymeric organic, inorganic, or organometallic molecule, and theterm “organic small molecule” refers to a non-polymer organic ororganometallic molecule. In OEL devices, small molecule materials can beused as emitter layers, as charge transport layers, as dopants inemitter layers (e.g., to control the emitted color) or charge transportlayers, and the like.

[0088] One suitable example of a transfer layer 200 for forming an OELdevice is illustrated in FIG. 3A. The transfer layer 200 includes ananode 202, an optional hole transport layer 204, an electrontransport/emitter layer 206, and a cathode 208. A separate electrontransport layer (not shown) can be included between emitter layer 206and cathode 208. Also, a separate electron blocking layer (not shown)can be included between the emitter layer and the anode, and a separatehole blocking layer (not shown) can be included between the emitterlayer and the cathode. Alternatively, either the cathode or anode can beprovided separately on a receptor (e.g., as a conductive coating on thereceptor, or as patterned conductive stripes or pads on the receptor)and not in the transfer layer. This is illustrated in FIG. 3B, for ananode-less transfer layer 200′ using primed reference numerals toindicate layers in common with the transfer layer 200.

[0089] The transfer layer 200 may also include one or more layers, suchas a release layer 210 and/or an adhesive layer 212, to facilitate thetransfer of the transfer layer to the receptor. Either of these twolayers can be conductive polymers to facilitate electrical contact witha conductive layer or structure on the receptor or conductive layer(s)formed subsequently on the transfer layer. It will be understood thatthe positions of the release layer and adhesive layer could be switchedwith respect to the other layers of the transfer layer so that thetransfer layer 200 can be transferred with either the anode or thecathode disposed proximate to the receptor surface.

[0090] For many applications, such as display applications, it ispreferred that at least one of the cathode and anode be transparent tothe light emitted by the electroluminescent device. This depends on theorientation of the device (i.e, whether the anode or the cathode iscloser to the receptor substrate) as well as the direction of lightemission (i.e., through the receptor substrate or away from the receptorsubstrate).

[0091] The anode 202 and cathode 208 are typically formed usingconducting materials such as metals, alloys, metallic compounds, metaloxides, conductive ceramics, conductive dispersions, and conductivepolymers, including, for example, gold, platinum, palladium, aluminum,titanium, titanium nitride, indium tin oxide (ITO), fluorine tin oxide(FTO), and polyaniline. The anode 202 and the cathode 208 can be singlelayers of conducting materials or they can include multiple layers. Forexample, an anode or a cathode may include a layer of aluminum and alayer of gold, a layer of aluminum and a layer of lithium fluoride, or ametal layer and a conductive organic layer. It may be particularlyuseful to provide a two-layer cathode (or anode) consisting of aconductive organic layer (e.g., 0.1 to 5 microns thick) and a thin metalor metal compound layer (e.g., 100 to 1000 Angstroms). Such a bilayerelectrode construction may be more resistant moisture or oxygen that candamage underlying moisture- or oxygen-sensitive layers in a device(e.g., organic light emitting layers). Such damage can occur when thereare pinholes in the thin metal layer, which can be covered and sealed bythe conductive organic layer. Damage and/or device failure can be causedby cracking or fracturing of the thin metal layer. Addition of aconductive organic layer can make the metal layer more resistant tofracture, or can act as a diffusion barrier against corrosive substancesand as a conductive bridge when fracturing occurs.

[0092] The hole transport layer 204 facilitates the injection of holesinto the device and their migration towards the cathode 208. The holetransport layer 204 can further act as a barrier for the passage ofelectrons to the anode 202. The hole transport layer 204 can include,for example, a diamine derivative, such asN,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (also known as TPD) orother hole conductive materials such as NPB. In general, the holdtransport layer can include organic small molecule materials, conductivepolymers, a polymer matrix doped with an organic small molecule, andother suitable organic or inorganic conductive or semiconductivematerials.

[0093] The electron transport/emitter layer 206 facilitates theinjection of electrons and their migration towards the anode 202. Theelectron transport/emitter layer 206 can further act as a barrier forthe passage of holes to the cathode 208. The electron transport/emitterlayer 206 is often formed from a metal chelate compound, such as, forexample, tris(8-hydroxyquinoline) aluminum (ALQ). Emitter layers (and/orelectron transport layers) can also include light emitting polymers suchas poly(phenylenevinylene)s (PPVs), poly-para-phenylens (PPPs), andpolyfluorenes (PFs); organic small molecule materials, of which ALQ isan example; polymers doped with organic small molecules; and othersuitable materials.

[0094] The interface between the hole transport layer 204 and electrontransport/emitter layer 206 forms a barrier for the passage of holes andelectrons and thereby creates a hole/electron recombination zone andprovides an efficient organic electroluminescent device. When theemitter material is ALQ, the OEL device emits blue-green light. Theemission of light of different colors may be achieved by the use ofdifferent emitters and dopants in the electron transport/emitter layer206 (see C. H. Chen et al., “Recent Developments in Molecular OrganicElectroluminescent Materials”, Macromolecular Symposia, 125, 1-48(1997), herein incorporated by reference).

[0095] Other OEL multilayer device constructions may be transferredusing different transfer layers. For example, the hole transportinglayer 204 in FIG. 3A could also be an emitter layer and/or the holetransporting layer 204 and the electron transporting/emitter layer 206could be combined into one layer. Furthermore, a separate emitter layercould be interposed between layers 204 and 206 in FIG. 3A.

[0096] Patterning OEL materials and layers to form OEL devices providesa particularly suited example to illustrate some difficulties withconventional patterning techniques and how these difficulties can beovercome according to the present invention. With conventionalpatterning techniques, there may be some materials or layers that cannotbe used due to susceptibility to attack, penetration, or dissolutionfrom exposure to solvents or etchants used coat or pattern other layerson the display substrate. Thus, there may be device and/or displayconstructions that cannot be made by conventional techniques because asolvent-coated layer would be coated on top of or next to asolvent-susceptible layer, or because an etchant would be used topattern layers on top of or next to other layers that are susceptible tothe etchant. For example, in forming an OEL device that includes ananode on a substrate, a small molecule hole transport layer on theanode, a light emitting polymer emitter on the hole transport layer, anda cathode on the emitter layer, the solvent used to coat the lightemitting polymer may damage the hole transport layer under conventionalprocessing techniques. The same limitations may hold for conventionalpatterning of adjacent OEL devices, one of which contains a lightemitting polymer emitter layer and the other of which contains anorganic small molecule emitter layer. These limitations can be overcomeusing thermal patterning methods of the present invention. Overcomingthese limitations allows a wider range of possible device constructionsand materials alternatives, and these in turn may be used to achieve OELdevices and displays that exhibit characteristics such as brightness,lifetime, color purity, efficiency, etc., that might not otherwise beachieved. Thus, the present invention provides new OEL device anddisplay constructions (as well as new patterning methods and new thermaltransfer donor elements).

[0097] Stacks of different types of OEL materials and/or organic chargetransport layers, as well as other device layers can be formed viathermal transfer from one or more donor elements. For example, a donorelement can be made that has a transfer layer that includes asolvent-coated layer (e.g., a light emitting polymer, a conductivepolymer, etc.) and a vapor-deposited or vacuum deposited layer (e.g.,organic small molecule emitter or charge transport layer, etc.). Thesolvent-coated layer can be any suitable material such as lightemitting-polymers, whether doped or un-doped, other solvent-coatableconductive, semiconductive, or insulative materials that can act aslight emitters, charge carriers (electron or hole transport), chargeinsulators (electron or hole blocking), color filters buffer layers, andthe like. The vapor-deposited layer can be any suitable materialincluding organic small molecule light emitters and/or charge carriers,other vapor deposited conductive or semiconductive organic or inorganicmaterials, insulative materials, and the like. An exemplary embodimentis one where the vapor deposited layer is coated over the solvent-coatedlayer as part of the transfer layer of a thermal transfer donor elementso that, when transferred to a receptor, the vapor deposited layer isdisposed between the solvent-coated material and the receptor. This isespecially useful when the vapor deposited material is incompatible withthe solvent of the solvent-coated material. Alternatively, differentand/or incompatible layers or stacks of layers can be thermallytransferred from separate donor elements to form multicomponent devicesor structures on a receptor. For example, a solvent-coated material canbe transferred on top of or next to a previously patterned material thatis incompatible with the solvent.

[0098] In general, multicomponent transfer layers of thermal transferdonor elements can be formed by coating individual layers according tothe following guidelines: vapor deposited organic small molecules orinorganic films can be deposited on top of any other layer type; solventborne small molecules or polymers can be deposited on metal films or anymaterial insoluble in the coating solvent; water borne small moleculesor polymers can be deposited on metal films or any material insoluble inthe aqueous solvent. These transfer layers can be patterned by selectivethermal transfer onto receptors, including receptors that have layerspreviously patterned or deposited thereon by any suitable method. Also,any layer type that can be thermally mass transferred from a donorelement can be transferred on top of or next to any other thermally masstransferred layers.

[0099] As discussed, OEL devices can be formed by selective thermaltransfer from one or more donor elements. Multiple devices can also betransferred onto a receptor to form, a pixilated display. As an example,an optical display can be formed as illustrated in FIGS. 4A through 4C.For example, green OEL devices 302 can be transferred onto the receptorsubstrate 300, as shown in FIG. 4A. Subsequently, blue OEL devices 304and then red OEL devices 306 may be transferred, as shown in FIGS. 4Band 4C. Each of the green, blue, and red OEL devices 302, 304, 306 aretransferred separately using green, blue, and red thermal transferelements, respectively. Alternatively, the red, green, and blue thermaltransfer elements could be transferred on top of one another to create amulti-color stacked OLED device of the type disclosed in U.S. Pat. No.5,707,745, herein incorporated by reference. Another method for forminga full color device includes depositing columns of hole transport layermaterial and then sequentially depositing red, green, and blue electrontransport layer/emitter multicomponent transfer units either parallel orperpendicular to the hole transport material. Yet another method forforming a full color device includes depositing red, green, and bluecolor filters (either conventional transmissive filters, fluorescentfilters, or phosphors) and then depositing multicomponent transfer unitscorresponding to white light or blue light emitters.

[0100] Still another method for forming multi-color pixilated OELdisplays is to pattern red, green, and blue emitters (for example) fromthree separate donors, and then, in a separate step, to pattern all thecathodes (and, optionally, electron transport layers) from a singledonor element. In this way, each OEL device is patterned by at least twothermal transfers, the first of which patterns the emitter portion (and,optionally, an adhesive layer, a buffer layer, anode, hole injectionlayer, hole transport layer, electron blocking layer, and the like), andthe second of which patterns the cathode portion (and, optionally, anelectron injection layer, electron transport layer, hole blocking layer,and the like). One advantage of splitting the device layers between twoor more donor elements (e.g., an emitter donor and a cathode donor) isthat the same donor elements can be used to pattern the emitter portionof OEL devices for either passive matrix or active matrix displayconstructions. Generally, active matrix displays include a commoncathode that is deposited over all the devices. For this construction,thermal transfer of an emitter stack that includes a cathode may not benecessary, and having a cathode-less transfer stack may be desirable.For passive matrix displays, cathode-less donors can be used to transfereach of the emitter portions (a different donor for each color, ifmulti-color is desired), followed by patterning of the cathodes for eachdevice from the same, separate donor element. Thus, various emitterdonors can be used for various display constructions, all while usingthe same, or similar, type of cathode donor.

[0101] Another advantage of the present invention is that OEL devices,for example, can be transferred and patterned according to the describedmethods to form adjacent devices having different, and otherwiseincompatible, types of emitter materials. For example, red-emittingorganic small molecule devices (e.g., that use an active vapor-depositedsmall molecule layer) can be patterned on the same receptor asblue-emitting light emitting polymer devices (e.g., that use an activesolution-coated light emitting polymer layer). This allows flexibilityto choose light-emitting materials (and other device layer materials)based on functionality (e.g., brightness, efficiency, lifetime,conductivity, physical properties after patterning (e.g., flexibility,etc.)) rather than on compatibility with the particular coating and/orpatterning techniques used for the other materials in the same oradjacent devices. The ability to choose different types of emittermaterials for different color devices in an OEL display can offergreater flexibility in choosing complementary device characteristics.The ability to use different types of emitters can also become importantwhen the preferred emitter material for one OEL device is incompatiblewith the preferred emitter material for another OEL device.

[0102] Referring again to FIG. 4, this example also illustrates otheradvantages of using thermal transfer elements to pattern multipledifferent devices on a receptor. For example, the. number of processingsteps can be reduced as compared to conventional photolithographymethods because many of the layers of each OEL device can be transferredsimultaneously, rather than using multiple etching and masking steps. Inaddition, multiple devices and patterns can be created using the sameimaging hardware. Only the thermal transfer element needs to be changedfor each of the different devices 302, 304, 306.

[0103] The receptor substrate may be any item suitable for a particularapplication including, but not limited to, transparent films, displayblack matrices, passive and active portions of electronic displays(e.g., electrodes, thin film transistors, organic transistors, etc.),metals, semiconductors, glass, various papers, and plastics.Non-limiting examples of receptor substrates which can be used in thepresent invention include anodized aluminum and other metals, plasticfilms (e.g., polyethylene terephthalate, polypropylene), indium tinoxide coated plastic films, glass, indium tin oxide coated glass,flexible circuitry, circuit boards, silicon or other semiconductors, anda variety of different types of paper (e.g., filled or unfilled,calendered, or coated). For OEL displays, the type of receptor usedoften depends on whether the display is a top emission display (devicespositioned between the viewer and the receptor substrate) or a bottomemission display (receptor substrate positioned between the viewer andthe devices). For a top emission display, the receptor need not betransparent. For a bottom emission display, a transparent receptorsubstrate is typically desired.

[0104] Various layers (e.g., an adhesive layer) may be coated onto thereceptor substrate to facilitate transfer of the transfer layer to thereceptor substrate. Other layers may be coated on the receptor substrateto form a portion of a multilayer device. For example, an OEL or otherelectronic device may be formed using a receptor substrate having ametal and/or conductive organic anode or cathode formed on the receptorsubstrate prior to transfer of the transfer layer from the thermaltransfer element. The anode or cathode may be formed, for example, bydeposition of one or more conductive layers on the receptor substrateand patterning of the layer into one or more anodes or cathodes usingany suitable method, for example, photolithographic techniques or thethermal transfer techniques taught herein.

[0105] A particularly useful receptor substrate for patterningmultilayer devices is one that has a common electrode or a pattern ofelectrodes along with a pattern of insulating barriers on top of theelectrode(s). The insulating barriers can be provided in a pattern thatcorresponds to the intended position of the edges of the multilayerdevices to help prevent electrical shorts between the receptorelectrode(s) and the opposing electrode transferred along with or on topof a multilayer stack. This is especially useful in passive matrixdisplays. Also, in active matrix display constructions, the insulatingbarriers can help isolate the transistors of the active matrix from thecommon electrode, which is generally provided. This can help preventleakage currents and parasitic capacitance which can reduce deviceefficiencies.

[0106] For example, FIG. 5A shows a cross-section of a receptor 500 thatincludes a substrate 501, a common electrode 502 disposed thereon, and aset of parallel insulating strips 504 disposed on the electrode 502.FIG. 5A also shows a donor element 510 that has a multicomponenttransfer layer 505 that includes at least two layers, an electrode layer508 and an emitter layer 506. Transfer layer 505 is to be transferred asparallel lines onto receptor 500 so that when an electric field isapplied between receptor electrode 501 and device electrode 508, emitterlayer 506 can emit light. As a practical matter (and in large part dueto the thinness of layers 506 and 508), portions of electrode layer 508at the edges of the transferred line may be likely to contact portionsof the receptor after transfer. If this happened, the emitter devicecould be rendered inoperable due to one or more electrical shorts. Thus,insulating barriers 504 can be patterned onto the receptor (by thermaltransfer or other suitable means) to cover areas where the edges of thetransfer layers will be positioned upon transfer. Thus, as shown in FIG.5B, if layer 508 overlaps layer 506 at the edges of a transferred line,layer 508 will contact insulating barrier 504, and the overall devicewill not short out due to contact with the underlying electrode 502 atthe edges. Insulating barriers can be used for both passive matrixdisplays and active matrix displays.

[0107] Another receptor substrate useful for patterning OEL devices isone that includes electrode pads for connecting the device cathodes tothe electronic driver system. For example, FIG. 6 shows a receptor 600for a passive matrix display that includes anodes 612 a, 612 b, 612 c,and so on patterned in parallel lines, and a plurality of contact pads602 a, 602 b, 602 c, 602 d, and so on, for connection to devicecathodes. Parallel lines can then be transferred from one or more donorelements to produce multilayer stacks 610 a, 610 b, 610 c, 610 d, and soon, to complete OEL devices. Each OEL device is positioned where ananode line and a multilayer stack line cross. At the cross portions, anemitter layer (an optional electron and hole transport and emitterlayers, as well as other layers) is disposed between an anode and acathode. Each line 610 terminates at one end adjacent an electrode pad602. Conductor material can then be deposited in and around areas 604 a,604 b, 604 c, 604 d, and so on, to connect the cathodes to the electrodepads, which in turn can be connected to the driver electronics.Conductor material can be deposited in areas 604 using any suitabletechnique include photolithography and mask-based vapor deposition.Alternatively, conductor material such as an organic conductor can beselectively transferred into areas 604 by thermal transfer from a donorelement. As described above, thermal transfer from a donor element canbe used to eliminate wet etching steps that may be required forphotolithographic or mask-based techniques. Thermally transferredorganic conductive layers can also be used to encapsulate the ends ofthe multilayer stacks, protecting the light emitting layers fromcorrosive agents. While FIG. 6 shows the situation for a passive matrixdisplay, the concept of thermally transferring an organic conductor toconnect a device to an electrode pad is equally applicable to activematrix displays.

EXAMPLES

[0108] In the following Examples, all of the vacuum deposited materialswere thermally evaporated and deposited at room temperature. Thedeposition rate and thickness of each vacuum deposited layer wasmonitored with a quartz crystal microbalance (Leybold Inficon Inc., EastSyracuse, N.Y.). The background pressure (chamber pressure prior to thedeposition) was roughly 1×10⁻⁵ torr (1.3×10⁻³ Pa).

[0109] The laser transfer system included a CW Nd:YAG laser,acousto-optic modulator, collimating and beam expanding optics, anoptical isolator, a linear galvonometer and an f-theta scan lens. TheNd:YAG laser was operating in the TEM 00 mode, and produced a totalpower of 7.5 Watts. Scanning was accomplished with a high precisionlinear galvanometer (Cambridge Technology Inc., Cambridge, Mass.). Thelaser was focused to a Gaussian spot with a measured diameter between100 μm and 140 μm at the 1/e² intensity level. The spot was heldconstant across the scan width by utilizing an f-theta scan lens. Thelaser spot was scanned across the image surface at a velocity of about 5meters/second. The f-theta scan lens held the scan velocity uniform towithin 0.1%, and the spot size constant to within ±3 microns.

Example 1 Preparation of a Substrate/LTHC/Interlayer Element

[0110] A carbon black light-to-heat conversion layer was prepared bycoating the following LTHC Coating Solution, according to Table 1, ontoa 0.1 mm PET substrate with a Yasui Seiki Lab Coater, Model CAG-150(Yasui Seiki Co., Bloomington, Ind.) using a microgravure roll of 381helical cells per lineal cm (150 helical cells per lineal inch). TABLE 1LTHC Coating Solution Parts by Component Weight Raven ™ 760 Ultra carbonblack pigment 3.39 (available from Columbian Chemicals, Atlanta, GA)Butvar ™ B-98 0.61 (polyvinylbutyral resin, available from Monsanto, St.Louis, MO) Joncryl ™ 67 1.81 (acrylic resin, available from S.C. Johnson& Son, Racine, WI) Elvacite ™ 2669 9.42 (acrylic resin, available fromICI Acrylics, Wilmington, DE) Disperbyk ™ 161 0.3 dispersing aid,available from Byk Chemie, Wallingford, CT) FC-430 ™ 0.012(fluorochemical surfactant, available from 3M, St. Paul, MN) Ebecryl ™629 14.13 (epoxy novolac acrylate, available from UCB Radcure, N.Augusta, SC) Irgacure ™ 369 0.95 (photocuring agent, available from CibaSpecialty Chemicals, Tarrytown, NY) Irgacure ™ 184 0.14 (photocuringagent, available from Ciba Specialty Chemicals, Tarrytown, NY) propyleneglycol methyl ether acetate 16.78 1-methoxy-2-propanol 9.8 methyl ethylketone 42.66

[0111] The coating was in-line dried at 40° C. and UV-cured at 6.1 n/minusing a Fusion Systems Model 1600 (400 W/in) UV curing system fittedwith H-bulbs (Fusion UV Systems, Inc., Gaithersburg, MD). The driedcoating had a thickness of approximately 3 microns.

[0112] Onto the carbon black coating of the light-to-heat conversionlayer was rotogravure coated an Interlayer Coating Solution, accordingto Table 2, using the Yasui Seiki Lab Coater, Model CAG-150 (Yasui SeikiCo., Bloomington, Ind.). This coating was in-line dried (40° C.) andUV-cured at 6.1 m/min using a Fusion Systems Model I600 (600 W/in)fitted with H-bulbs. The thickness of the resulting interlayer coatingwas approximately 1.7 microns. TABLE 2 Interlayer Coating SolutionComponent Parts by Weight Butvar ™ B-98 0.98 Joncryl ™ 67 2.95Sartomer ™ SR351 ™ 15.75 (trimethylolpropane triacrylate, available fromSartomer, Exton, PA) Irgacure ™ 369 1.38 Irgacure ™ 184 0.21-methoxy-2-propanol 31.5 methyl ethyl ketone 47.24

Example 2 Preparation or Another Substrate/LTHC/Interlayer Element

[0113] A carbon black light-to-heat conversion layer was prepared bycoating the following LTHC Coating Solution, according to Table 3, ontoa 0.1 mm PET substrate with a Yasui Seiki Lab Coater, Model CAG-150(Yasui Seiki Co., Bloomington, Ind.) using a microgravure roll of 228.6helical cells per lineal cm (90 helical cells per lineal inch). TABLE 3LTHC Coating Solution Parts by Component Weight Raven ™ 760 Ultra carbonblack pigment 3.78 (available from Columbian Chemicals, Atlanta, GA)Butvar ™ B-98 0.67 (polyvinylbutyral resin, available from Monsanto, St.Louis, MO) Joncryl ™ 67 2.02 (acrylic resin, available from S.C. Johnson& Son, Racine, WI) Disperbyk ™ 161 0.34 (dispersing aid, available fromByk Chemie, Wallingford, CT) FC-430 ™ 0.01 (fluorochemical surfactant,available from 3M, St. Paul, MN) SR 351 ™ 22.74 (trimethylolpropanetriacrylate, available from Sartomer, Exton, PA) Duracure ™ 1173 1.48(2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator, available fromCiba, Hawthorne, NY) 1-methoxy-2-propanol 27.59 methyl ethyl ketone41.38

[0114] The coating was in-line dried at 40° C. and UV-cured at 6.1 m/minusing a Fusion Systems Model I600 (400 W/in) UV curing system fittedwith H-bulbs. The dried coating had a thickness of approximately 3microns.

[0115] Onto the carbon black coating of the light-to-heat conversionlayer was 10 rotogravure coated an Interlayer Coating Solution,according to Table 4, using the Yasui Seiki Lab Coater, Model CAG-150(Yasui Seiki Co., Bloomington, Ind.). This coating was in-line dried(40° C.) and UV-cured at 6.1 m/min using a Fusion Systems Model 1600(600 W/in) fitted with H-bulbs. The thickness of the resultinginterlayer coating was approximately 1.7 microns. TABLE 4 InterlayerCoating Solution Component Parts by Weight Butvar ™ B-98 0.99 Joncryl ™67 2.97 SR 351 ™ 15.84 Duracure ™ 1173 0.99 1-methoxy-2-propanol 31.68methyl ethyl ketone 47.52

Example 3 Hole Transport Thermal Transfer Element

[0116] A hole transport thermal transfer element was formed using thesubstrate/LTHC/interlayer element of Example 1. A hole transport coatingsolution, formed by mixing the components of Table 5, was coated ontothe interlayer using a #6 Mayer bar. The coating was dried for 10 min at60° C. TABLE 5 Hole Transport Coating Solution Parts by Component WeightN,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine 2.5 polyvinylcarbazole2.5 cyclohexanone 97.5 propylene glycol methyl ether acetate (PGMEA)97.5

Example 4 OEL Small Molecule Thermal Transfer Element

[0117] An OEL thermal transfer element with a multicomponent transferlayer was pre pared by applying coatings to a substrate/LTHC/interlayerelement formed according to Example 1. A 200 Å layer of copperphthalocyanine w as deposited on the interlayer as a semiconductingrelease layer. Next, a 250 Å layer of aluminum was deposited as acathode layer. A 10 Å layer of lithium fluoride was deposited on thealuminum. Next, a 300 Å layer of tris(8-hydroxyquinolinato) aluminum(ALQ) was deposited as an electron transport layer. Finally, a 200 Ålayer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) wasdeposited as a hole transport layer.

Example 5 Preparation of an OEL Small Molecule Device

[0118] A receptor substrate of glass covered with indium tin oxide (ITO)(resistivity of 10 Ω/square, Thin Film Devices Inc., Anaheim, Calif.)was used to form the anode of the OEL device. First, the hole transportthermal transfer element of Example 3 was imaged onto the receptor. Thiswas followed by imaging of the OEL small molecule thermal transferelement of Example 4 to complete the OEL device.

[0119] In each transfer, the transfer layer side of the thermal transferelement was held in intimate contact with the receptor in a vacuumchuck. A laser was directed to be incident upon the substrate side ofthe thermal transfer elements. The exposures were performed so that thetwo transfer layers were transferred with correct registration. Thisproduced 120 μm wide lines. The final OEL device had layers in thefollowing order (from top to bottom):

[0120] Aluminum Cathode

[0121] Lithium Fluoride

[0122] ALQ Electron Transport Layer/Emitter

[0123] TPD Hole Transport Layer (from OEL thermal transfer element)

[0124] TPD Hole Transport Layer (from hole transport thermal transferelement)

[0125] ITO and Glass Receptor

[0126] Electrical contact was made at the ITO anode and the aluminumcathode.

[0127] When a potential was applied, the OEL device produced visuallydetectable light.

[0128] The injection current was monitored as a function of the appliedpotential (voltage) which was continuously swept from 0 volts to 10-30volts. At one point 70 μA at 10 volts flowing through a 42 mm×80 μmdevice was measured. This corresponds to a current density of about 2mA/cm². The current density is well within the normal operating range ofsmall molecule devices fabricated directly onto a receptor substrateusing conventional techniques.

Example 6 Another OEL Small Molecule Thermal Transfer Element

[0129] An OEL thermal transfer element with a multicomponent transferlayer was prepared by applying coatings to a substrate/LTHC/interlayerelement prqpared according to Example 1. A primer solution, according toTable 6, was first coated using a #3 Mayer bar. The coating was dried atabout 60° C. for about 5 minutes. TABLE 6 Primer Solution Parts byComponent Weight PVP K-90 (polyvinyl pyrrolidone, International 2Specialty Products, Wayne, NJ) PVA Gohsenol KL-03 (polyvinyl alcohol,Nippon 2 Gohsci, Osaka, Japan) Elvacite 2776 (acrylic polymer, ICIAcrylics) 4 DMEA (dimethylethanolamine, Aldrich) 0.8 2-butoxyethanol(Aldrich) 0.8 deionized water 150.4

[0130] A 200 Å layer of copper phthalocyanine was deposited as asemiconducting release layer on the primer layer. Next, a 250 Å layer ofaluminum was deposited as a cathode layer. A 10 Å layer of lithiumfluoride was deposited on the aluminum. Next, a 300 Å layer of ALQ wasdeposited as an electron transport layer. Finally, a 200 Å layer of TPDwas deposited as a hole transport layer.

Example 7 Transfer of a Partial OEL Small Molecule Transfer Layer to aFlexible Substrate

[0131] The receptor substrate consisted of a piece of 4 mil (about 100μm) PET film (unprimed HPE100, Teijin Ltd., Osaka, Japan). First, thehole transport thermal transfer element of Example 3 was imaged onto thereceptor. Then the OEL thermal transfer element of Example 6 was imagedonto the hole transport layer.

[0132] In each transfer, the transfer layer side of the thermal transferelement was held in intimate contact with the receptor in a vacuumchuck. A laser was directed to be incident upon the substrate side ofthe thermal transfer elements. The exposures were performed so that thetwo layers with correct registration. This produced 120 μm wide lines.The final construction had layers in the following order (from top tobottom):

[0133] Aluminum Cathode

[0134] Lithium Fluoride

[0135] ALQ Electron Transport Layer/Emitter

[0136] TPD Hole Transport Layer (from OEL Thermal Transfer Element)

[0137] TPD Hole Transport Layer (from hole transport thermal transferelement)

[0138] PET Receptor

Example 8 OEL Light Emitting Polymer Thermal Transfer Element

[0139] An OEL thermal transfer element with a multicomponent transferlayer was prepared by applying coatings to a substrate/LTHC/interlayerelement formed according to Example 1. A 100 Å layer of copperphthalocyanine was deposited on the interlayer as a release layer. Next,a 450 Å layer of aluminum was deposited as a cathode layer. A lightemitting polymer coating solution was then prepared by adding 2% byweight of poly(9,9-di-n-octylfluorene) (designated “PFC8” in theseExamples) in toluene and then diluting the solution with MEK until a 1%by weight concentration of PFC8 was achieved. PFC8 is a blue emittingpolyfluorene material that has a chemical structure as shown below, andthat can be synthesized according to the methods disclosed in U.S. Pat.No. 5,777,070, which is incorporated into this document.

[0140] The coating solution was hand coated onto the aluminum layerusing a #6 Mayer bar and dried to form a 1000 Å layer of PFC8 as a bluelight emitting layer. Finally, a 500 Å layer of NPB was deposited as ahole transport layer.

Example 9 Another OEL Light Emitting Polymer Thermal Transfer Element

[0141] An OEL thermal transfer element with a multicomponent transferlayer was prepared by applying coatings to a substrate/LTHC/interlayerelement formed according to Example 1. A 100 Å layer of copperphthalocyanine was deposited on the interlayer as a release layer. Next,a 450 Å layer of aluminum was deposited as a cathode layer. A lightemitting polymer coating solution was then prepared by adding 2% byweight of a copolymer of PFC8 and benzothiadiazole (copolymer designated“PFC8/BDTZ” in these Examples) in toluene and then diluting the solutionwith MEK until a 1% by weight concentration of PFC8/BTDZ copolymer wasachieved. PFC8/BDTZ is a green light emitting polyfluorene copolymer.The coating solution was hand coated onto the aluminum layer using a #6Mayer bar and dried to form a 1000 Å layer of PFC8/BTDZ as a green lightemitting layer. Finally, a 500 Å layer of NPB was deposited as a holetransport layer.

Example 10

[0142] Preparation of an OEL Light Emitting Polymer Device

[0143] A receptor substrate of glass covered with ITO (resistivity of 10Ω/square, Thin Film Devices Inc., Anaheim, Calif.) was used to form theanode of the OEL devices. The ITO covered glass was then spin coated at3000 r.p.m. with an aqueous solution of 2.5% by weight polypyrrole (soldunder the trade designation Baytron-P, Bayer Corp., Pittsburgh, Pa.).The polypyrrole coating was then dried at 80° C. for 5 minutes to form abuffer layer on the receptor substrate.

[0144] A blue light emitting polymer device was formed when the thermaltransfer element of Example 8 was imaged onto the receptor. The transferlayer side of the thermal transfer element of Example 8 was held inintimate contact with the receptor in a vacuum chuck. A laser wasdirected to be incident upon the substrate side of the thermal transferelement, using a dose of 0.6 J/cm². This produced 100 μm wide lines. Thefinal OEL device had layers in the following order (from top to bottom):

[0145] Aluminum Cathode

[0146] PFC8 Blue Light Emitting Polymer Layer

[0147] NPB Hole Transport Layer

[0148] Polypyrrole Buffer Layer (coated directly onto the receptor)

[0149] ITO and Glass Receptor

[0150] Electrical contact was made at the ITO anode and the aluminumcathode. When a potential was applied, the OEL device produced visuallydetectable blue light.

Example 11 Preparation of another OEL Light Emitting Polymer Device

[0151] A receptor substrate of glass covered with ITO (resistivity of 10Ω/square, Thin Film Devices Inc., Anaheim, Calif.) was used to form theanode of the OEL devices. The ITO covered glass was then spin coated at3000 r.p.m. with an aqueous solution of 2.5% by weight polypyrrole. Thepolypyrrole coating was 'then dried at 80° C. for 5 minutes to form abuffer layer on the receptor substrate.

[0152] A green light emitting polymer device was formed when the thermaltransfer element of Example 9 was imaged onto the receptor. The transferlayer side of the thermal transfer element of Example 9 was held inintimate contact with the receptor in a vacuum chuck. A laser wasdirected to be incident upon the substrate side of the thermal transferelement, using a dose of 0.6 J/cm². This produced 100 μm wide lines. Thefinal OEL device had layers in the following order (from top to bottom):

[0153] Aluminum Cathode

[0154] PFC8/BTDZ Green Light Emitting Polymer Layer

[0155] NPB Hole Transport Layer

[0156] Polypyrrole Buffer Layer (coated directly onto the receptor)

[0157] ITO and Glass Receptor

[0158] Electrical contact was made at the ITO anode and the aluminumcathode. When a potential was applied, the OEL device produced visuallydetectable blue light.

[0159] Examples 8-11 demonstrate that OEL devices that havesolvent-coated light emitting polymer layers disposed on top ofvacuum-deposited organic small molecule layers can be patterned ontosubstrates. This was accomplished by forming donor elements that hadorganic small molecule material vapor coated onto dried solvent-coatedlight emitting polymer layers, and then selectively transferring the.multicomponent transfer stack to a receptor substrate.

Example 12 Cathode Layer Thermal Transfer Element

[0160] A cathode layer thermal transfer element was formed using thesubstrate/LTHC/interlayer element of Example 1. A 100 Å layer of copperphthalocyanine was deposited on the interlayer as a release layer. Next,a 450 Å layer of aluminum was deposited as a cathode layer. Finally, a500 A layer of3-(4-Biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ-01)was deposited on the aluminum layer as an organic small moleculeelectron transport/adhesion promoting layer.

Example 13 Light Emitting Polymer Thermal Transfer Element

[0161] A light emitting polymer thermal transfer element with a singlecomponent transfer layer was prepared. A light emitting polymer coatingsolution was prepared by adding 2% by weight of PFC8 in toluene and thendiluting the solution with MEK until a 1% by weight concentration ofPFC8 was achieved. The coating solution was hand coated onto to theinterlayer of a substrate/LTHC/interlayer element (formed according toExample 1) using a #6 Mayer bar. The coating was dried to form a 1000 Åpolyfluorene transfer layer.

Example 14 Another Light Emitting Polymer Thermal Transfer Element

[0162] A light emitting polymer thermal transfer element with a singlecomponent transfer layer was prepared. A light emitting polymer coatingsolution was prepared by adding 2% by weight of PFC8/BTDZ in toluene andthen diluting the solution with MEK until a 1% by weight concentrationof PFC8/BTDZ was achieved. The coating solution was hand coated onto tothe interlayer of a substrate/LTHC/interlayer element (formed accordingto Example 1) using a #6 Mayer bar. The coating was dried to form a 1000A polyfluorene transfer layer.

Example 15 Preparation of an OEL Light Emitting Polymer Device

[0163] A receptor substrate of glass covered with ITO (resistivity of 10Ω/square, Thin Film Devices Inc., Anaheim, Calif.) was used to form theanode of the OEL devices. The ITO covered glass was then spin coated at3000 r.p.m. with an aqueous solution of 2.5% by weight polypyrrole. Thepolypyrrole coating was then dried at 80° C. for 5 minutes to form abuffer layer on the receptor substrate.

[0164] The thermal transfer element of Example 13 was imaged onto thereceptor to form 100 μm wide lines of a blue light emitting polymermaterial on the polypyrrole buffer layer. The transfer layer side of thethermal transfer element of Example 13 was held in intimate contact withthe receptor in a vacuum chuck. A laser was directed to be incident uponthe substrate side of the thermal transfer element, using a dose of 0.6J/cm². Next, the cathode thermal transfer element of Example 12 wasimaged onto the receptor to form 100 μm wide lines on top of and inregistry with the lines of light emitting polymer material previouslytransferred. The transfer layer side of the thermal transfer element ofExample 12 was held in intimate contact with the receptor in a vacuumchuck. A laser was directed to be incident upon the substrate side ofthe thermal transfer element, using a dose of 0.6 J/cm².

[0165] The final OEL device had layers in the following order (from topto bottom):

[0166] Aluminum Cathode

[0167] TAZ-01 Electron Transport Layer

[0168] PFC8 Blue Light Emitting Polymer Layer

[0169] Polypyrrole Buffer Layer (coated directly onto the receptor)

[0170] ITO and Glass Receptor

[0171] Electrical contact was made at the ITO anode and the aluminumcathode. When a potential was applied, the OEL device produced visuallydetectable blue light.

Example 16 Preparation of another OEL Light Emitting Polymer Device

[0172] A receptor substrate of glass covered with ITO (resistivity of 10Ω/square, Thin Film Devices Inc., Anaheim, Calif.) was used to form theanode of the OEL devices. The ITO covered glass was then spin coated at3000 r.p.m. with an aqueous solution of 2.5% by weight polypyrrole. Thepolypyrrole coating was then dried at 80° C. for 5 minutes to form abuffer layer on the receptor substrate.

[0173] The thermal transfer element of Example 14 was imaged onto thereceptor to form 100 μm wide lines of a green light emitting polymermaterial on the polypyrrole buffer layer. The transfer layer side of thethermal transfer element of Example 14 was held in intimate contact withthe receptor in a vacuum chuck. A laser was directed to be incident uponthe substrate side of the thermal transfer element, using a dose of 0.6J/cm². Next, the cathode thermal transfer element of Example 12 wasimaged onto the receptor to form 100 μm wide lines on top of and inregistry with the lines of light emitting polymer material previouslytransferred. The transfer layer side of the thermal transfer element ofExample 12 was held in intimate contact with the receptor in a vacuumchuck. A laser was directed to be incident upon the substrate side ofthe thermal transfer element, using a dose of 0.6 J/cm².

[0174] The final OEL device had layers in the following order (from topto bottom):

[0175] Aluminum Cathode

[0176] TAZ-01 Electron Transport Layer

[0177] PFC8/BTDZ Green Light Emitting Polymer Layer

[0178] Polypyrrole Buffer Layer (coated directly onto the receptor)

[0179] ITO and Glass Receptor

[0180] Electrical contact was made at the ITO anode and the aluminumcathode. When a potential was applied, the OEL device produced visuallydetectable green light.

[0181] Examples 12-16 demonstrate that the same cathode donor elementcan be used to pattern cathode layers on top of different emitterlayers, previously patterned, to form OEL devices.

Example 17 Preparation of Small Molecule and Light Emitting Polymer OELDevices on the Same Receptor Substrate

[0182] This Example demonstrates that functional OEL devices that havelight emitting polymer emitter layers and OEL devices that have organicsmall molecule emitter layers can be patterned next to each other onreceptor substrates.

[0183] A thermal transfer element with a multicomponent transfer layerhaving a green light small molecule emitter (“Green SM Donor”) wasprepared by applying coatings to a substrate/LTHC/interlayer elementformed according to Example 1. A 100 Å layer of copper phthalocyaninewas deposited on the interlayer as a release layer. Next, a 450 Å layerof aluminum was deposited as a cathode layer. A 10 Å layer of lithiumfluoride was deposited on the aluminum. Next, a 500 Å layer of ALQ wasdeposited as an electron transport layer. Finally, a 500 Å layer of NPBwas deposited as a hole transport layer.

[0184] A thermal transfer element with a multicomponent transfer layerhaving a red light small molecule emitter (“Red SM Donor”) was preparedby applying coatings to a substrate/LTHC/interlayer element formedaccording to Example 1. A 100 Å layer of copper phthalocyanine wasdeposited on the interlayer as a release layer. Next, a 450 Å layer ofaluminum was deposited as a cathode layer. A 10 Å layer of lithiumfluoride was deposited on the aluminum. Next, a 500 Å layer of ALQ wasdeposited as an electron transport layer. Next, a layer of platinum octaethyl porphyrin (PtOEP) was vapor deposited on the ALQ layer as adopant. The PtOEP dopant was deposited to achieve a 2 to 3% by weightconcentration of the dopant in the ALQ emitter layer. Finally, a 500 Ålayer of NPB was deposited as a hole transport layer.

[0185] A thermal transfer element was made according to Example 8 toproduce a donor element having a blue light emitting polymer emitter(“Blue LEP Donor”). A thermal transfer element was made according toExample 9 to produce a donor element having a green light emittingpolymer emitter (“Green LEP Donor”).

[0186] A receptor substrate of glass covered with ITO (resistivity of 10Ω/square, Thin Film Devices Inc., Anaheim, Calif.) was used to form theanode of the OEL devices. The ITO covered glass was then spin coated at3000 r.p.m. with an aqueous solution of 2.5% by weight polypyrrole. Thepolypyrrolc coating was then dried at 80° C. for 5 minutes to form abuffer layer on the receptor substrate.

[0187] The Blue LEP Donor was imaged onto the receptor substrate to forma series of parallel lines. Next, the Red SM Donor was imaged onto thesame receptor for form a series of parallel lines, each line positionedbetween lines transferred from the Blue LEP Donor. Electrical contactwas made at the ITO anodes and aluminum cathodes. Visibly detected bluelight was emitted from the lines patterned from the Blue LEP Donor andvisibly detected red light was emitted from the lihes patterned from theRed SM Donor.

[0188] The Green LEP Donor was then imaged onto another receptorsubstrate to form a series of parallel lines. Next, the Green SM Donorwas imaged onto the same receptor for form a series of parallel lines,each line positioned between lines transferred from the Green LEP Donor.Electrical contact was made at the ITO anodes and aluminum cathodes.Visibly detected green light was emitted from the lines patterned fromthe Green LEP Donor and visibly detected green light was emitted fromthe lines patterned from the Green SM Donor.

Example 18 Preparation of Red, Green, and Blue OEL Devices on the SameReceptor Substrate

[0189] This Example demonstrates that functional red, green, and blueOEL devices can be patterned next to each other on the same receptorsubstrate.

[0190] A thermal transfer element with a multicomponent transfer layerhaving a blue light small molecule emitter (“Blue SM Donor”) wasprepared by applying coatings to a substrate/LTHC/interlayer elementformed according to Example 1. A 100 Å layer of copper phthalocyaninewas deposited on the interlayer as a release layer. Next, a 450 Å layerof aluminum was deposited as a cathode layer. A 10 Å layer of lithiumfluoride was deposited on the aluminum. Next, a 500 Å layer ofBis(2-methyl-8-quinolinolato)(para-phenyl-phenolato)aluminum (BAlq) wasdeposited as an electron transport/emitter layer. The BAlq wassynthesized as described in U.S. Pat. No. 5,141,671, the disclosure ofwhich is incorporated into this document. Next, a layer of perylene wasvapor deposited on the BAlq layer as a dopant. The perylene dopant wasdeposited to achieve a 2 to 3% by weight concentration of the dopant inthe BAlq emitter layer. Finally, a 500 Å layer of NPB was deposited as ahole transport layer.

[0191] A receptor substrate of glass covered with ITO (resistivity of 10Ω/square, Thin Film Devices Inc., Anaheim, Calif.) was used to form theanode of the OEL devices. The ITO covered glass was then spin coated at3000 r.p.m. with an aqueous solution of 2.5% by weight polypyrrole. Thepolypyrrole coating was then dried at 80° C. for 5 minutes to form abuffer layer on the receptor substrate.

[0192] The Red SM Donor of Example 17, the Green SM Donor of Example 17,and the Blue SM Donor of this Example were successively imaged onto thereceptor substrate to form a series of parallel lines. The lines werepatterned so that a line transferred from one donor was positionedbetween lines transferred from each of the other two donors. Electricalcontact was made at the ITO anodes and aluminum cathodes. Visiblydetected green light was emitted from the lines patterned from the GreenSM Donor, visibly detected red light was emitted from the linespatterned from the Red SM Donor, and visibly detected blue light wasemitted from the lines patterned from the Blue SM Donor.

[0193] The present invention should not be considered limited to theparticular examples described above, but rather should be understood tocover all aspects of the invention as fairly set out in the attachedclaims. Various modifications, equivalent processes, as well as numerousstructures to which the present invention may be applicable will bereadily apparent to those of skill in the art to which the presentinvention is directed upon review of the instant specification.

What is claimed is:
 1. A method for making an organic electroluminescentdevice comprising thermally transferring a light emitting polymer layerand a small molecule layer from one or more thermal transfer donorelements to a receptor so that the light emitting polymer layer and thesmall molecule layer are disposed between an anode and a cathode on thereceptor.
 2. A thermal transfer donor element for use in making organicelectroluminescent devices, comprising in the following order: asubstrate; a light-to-heat conversion layer; an interlayer; and athermal transfer layer including, in the following order, a releaselayer, a cathode layer, a light emitting polymer layer, a small moleculehole transport layer, and an anode layer.
 3. A method for patterning afirst material and a second material on a receptor, which methodcomprises selectively thermal transferring the first material proximateto the second material on the receptor from a first donor element, thefirst material being formed on the donor element by solution coatingusing a solvent, the second material being incompatible with saidsolvent, wherein at least one of the first and second materialscomprises an organic electroluminescent material, an organic conductor,or an organic semiconductor.
 4. The method of claim 1, wherein the firstmaterial comprises a light emitting polymer.
 5. The method of claim 1,wherein the second material comprises an organic small moleculematerial.
 6. The method of claim 1, further comprising selectivelythermal transferring the second material on the receptor from a seconddonor element.
 7. The method of claim 1, wherein the second material isselectively thermal transferred along with the first material from thefirst donor sheet to the receptor.
 8. The method of claim 1, wherein thefirst material is transferred next to the second material on thereceptor.
 9. The method of claim 1, wherein after transfer the secondmaterial is disposed between the first material and the receptor. 10.The method of claim 1, wherein the step of selectively thermaltransferring the first material from the first donor element comprisesselectively heating the first donor element using a thermal print head.11. The method of claim 1, wherein the first donor element comprises asubstrate and a light-to-heat conversion layer disposed between thesubstrate and the first material, and wherein the step of selectivelythermal transferring the first material comprises selectively exposingthe first donor element to imaging radiation.
 12. A method forpatterning materials comprising the steps of: forming a donor elementcomprising a donor substrate and a multicomponent thermal transferlayer, the thermal transfer layer having at least a first layercomprising a solvent-coated material and a second layer comprising asolvent-susceptible material, the solvent-susceptible material beingincompatible with the solvent used to coat the solvent-coated material,wherein the first layer is disposed between the second layer and thedonor substrate; placing the thermal transfer layer proximate areceptor; and selectively thermally transferring the multicomponenttransfer layer from the donor element to the receptor, wherein at leastone of the solvent-coated material and the solvent-susceptible materialcomprises an organic electroluminescent material, an organic conductor,or an organic semiconductor.
 13. The method of claim 12, wherein thefirst layer comprises a light emitting polymer.
 14. The method of claim12, wherein the second layer comprises an organic small moleculematerial.
 15. The method of claim 12, wherein the thermal transfer layercomprises a conductor layer, a light emitting polymer layer, and a smallmolecule layer.
 16. The method of claim 12, wherein the donor elementcomprises a substrate, a light-to-heat conversion layer disposed betweenthe substrate and the thermal transfer layer, and an interlayer disposedbetween the light-to-heat conversion layer and the thermal transferlayer.
 17. The method of claim 16, wherein the donor element furthercomprises a release layer disposed between the interlayer and thethermal transfer layer.
 18. The method of claim 17, wherein the releaselayer comprises copper phthalocyanine.
 19. The method of claim 12,wherein the step of selectively thermally transferring comprisesselectively heating the donor element using a thermal print head. 20.The method of claim 12, wherein the step of selectively thermallytransferring comprises selectively exposing the donor element to imagingradiation, the donor element including a radiation absorber forconverting the imaging radiation into heat.
 21. A method for patterningmaterials comprising the steps of: thermally transferring selectedportions of a first transfer layer from a first donor element to areceptor, the first transfer layer containing a first material, thefirst material being solution-coated from a solvent onto the firstdonor; and thermally transferring selected portions of a second transferlayer from a second donor element to the receptor, the second transferlayer containing a second material, the second material beingincompatible with the solvent, wherein at least one of the first andsecond materials comprises an organic electroluminescent material, anorganic conductor, or an organic semiconductor.
 22. The method of claim21, wherein the first transfer layer comprises multiple layers.
 23. Themethod of claim 21, wherein the second transfer layer comprises multiplelayers.
 24. The method of claim 21, wherein the first material comprisesa light emitting polymer.
 25. The method of claim 21, wherein the secondmaterial comprises a light emitting organic small molecule.
 26. A methodfor making a thermal transfer donor element, which method comprisesforming a donor element that has a donor substrate and a transfer layer,the transfer layer being formed by (a) solution coating a first materialusing a solvent, (b) drying the first material to substantially removethe solvent, and (c) depositing a second material such that the firstmaterial is disposed between the donor substrate and the secondmaterial, the second material being incompatible with the solvent usedto coat the first material.
 27. The method of claim 26, wherein thefirst material comprises a light emitting polymer.
 28. The method ofclaim 26, wherein the second material comprises an organic smallmolecule material.
 29. An organic electroluminescent display comprising:a first organic electroluminescent device disposed on a displaysubstrate, the first organic electroluminescent device having an emitterlayer that is a light emitting polymer; and a second organicelectroluminescent device disposed on the display substrate, the secondorganic electroluminescent device having an emitter layer that is anorganic small molecule material.
 30. An organic electroluminescentdisplay comprising an organic electroluminescent device disposed on adisplay substrate, the organic electroluminescent, device comprising, inthe following order from the substrate, a first electrode, a smallmolecule charge transport layer, a polymer emitter layer, and a secondelectrode.